<template>
  <div>
    <router-link tag="div" to="/" class="header-abs" v-show="showAbs">
      <span class="iconfont header-abs-back">&#xe624;</span>
    </router-link>
    <div class="header-fixed" v-show="!showAbs" :style="opcityStyle">
      <router-link to="/">
        <span class="iconfont header-fixed-back">&#xe624;</span>
      </router-link>
      英雄详情
    </div>
  </div>
</template>

<script>
import { ref, onMounted, onUnmounted, reactive } from '@vue/runtime-core'
export default {
  name: 'DetailHeader',
  setup () {
    let showAbs = ref(true)
    let opcityStyle = reactive({ opacity: 0 })
    function handleScroll () {
      const top = document.documentElement.scrollTop || document.body.scrollTop || window.pageYOffset
      if (top > 60) {
        let opacity = top / 140
        opacity = opacity > 1 ? 1 : opacity
        opcityStyle.opacity = opacity
        showAbs.value = false
      } else {
        showAbs.value = true
      }
    }
    onMounted(() => { window.addEventListener('scroll', handleScroll) })
    onUnmounted(() => { window.removeEventListener('scroll', handleScroll) })
    return { showAbs, opcityStyle }
  }
}
</script>

<style lang='stylus' scoped>
@import '~styles/varibles.styl'
.header-abs
  position absolute
  left 0.2rem
  top 0.2rem
  width 0.8rem
  height 0.8rem
  line-height 0.8rem
  border-radius 0.4rem
  text-align center
  background rgba(0, 0, 0, 0.8)
  .header-abs-back
    color #fff
    font-size 0.4rem
.header-fixed
  z-index 2
  position fixed
  top 0
  left 0
  right 0
  height $headerHeight
  line-height $headerHeight
  text-align center
  color #fff
  background $bgColor
  font-size 0.32rem
  .header-fixed-back
    position absolute
    top 0
    left 0
    width 0.64rem
    text-align center
    font-size 0.4rem
    color #fff
</style>
